docs: Update documentation for auto-update system and integration tests

.github/copilot-instructions.md

@@ -19,6 +19,7 @@ WebDrop Bridge is a professional Qt-based desktop application that converts web-
 | `src/webdrop_bridge/config.py` | Configuration management |
 | `src/webdrop_bridge/core/validator.py` | Path validation and security |
 | `src/webdrop_bridge/core/drag_interceptor.py` | Drag-and-drop handling |
+| `src/webdrop_bridge/core/updater.py` | Update check and release management |
 | `src/webdrop_bridge/ui/main_window.py` | Main Qt window |
 | `tests/` | Pytest-based test suite |
 | `pyproject.toml` | Modern Python packaging |
@@ -36,11 +37,11 @@ WebDrop Bridge is a professional Qt-based desktop application that converts web-
 ```python
 def validate_path(path: Path, allowed_roots: List[Path]) -> bool:
     """Validate path against allowed roots.
-    
+
     Args:
         path: File path to validate
         allowed_roots: List of allowed root directories
-        
+
     Returns:
         True if path is valid, False otherwise
     """
@@ -102,6 +103,12 @@ bash build/scripts/build_macos.sh      # macOS
 - `LocalContentCanAccessFileUrls`: True (required for drag)
 - `LocalContentCanAccessRemoteUrls`: False (prevent phishing)
 
+### Update Flow
+- UpdateManager checks for new releases via Forgejo API.
+- Caching is used to avoid redundant network calls.
+- Only newer versions trigger update signals.
+- Release notes and assets are parsed and preserved.
+
 ### Cross-Platform
 - Use PySide6 APIs that work on both Windows and macOS
 - Test on both platforms when possible
@@ -114,9 +121,10 @@ bash build/scripts/build_macos.sh      # macOS
 tests/unit/test_validator.py
 tests/unit/test_drag_interceptor.py
 
-# Integration tests: Component interaction
+# Integration tests: Component interaction and update flow
 tests/integration/test_drag_workflow.py
 tests/integration/test_end_to_end.py
+tests/integration/test_update_flow.py
 
 # Fixtures: Reusable test data
 tests/conftest.py
@@ -136,6 +144,7 @@ Target: 80%+ code coverage
 - **Public APIs**: Docstrings required
 - **Modules**: Add docstring at top of file
 - **Features**: Update README.md and docs/
+- **Integration tests**: Reference and document in README.md and docs/ARCHITECTURE.md
 - **Breaking changes**: Update DEVELOPMENT_PLAN.md
 
 ## Git Workflow